Truck concentrator for telephone answering service



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TRUCK coNcENTRAToR Foa TELEPHONE ANswERING SERVICE Filed Sept. 29, 1958 18 Sheets-Shea?l 13 FIG. [2A PUL SEAMPL /F/ER (P) GIA/LESS OTHERWISE SPECIFIED RES/MNCE VALUES ARE IN OHMS, CAPAC/TNCE VALUES ARE IN MICROFAPADS) ICT 4.5M MIN. INPUT L FLL ls-lau OUTPUT 24 u /Nl/ENTOR BV M. E. KROM www A 7` TOR/VE V Sept. 26, 1961 M. E. KRoM 3,002,054

TRUCK coNcENTRAToR FoR TELEPHONE ANswERING SERVICE Filed sept. 29, 1958 18 sheets-sheet 14 F G. /3A AMPL /F/ER (Rs) (UNLESS OTHERWISE SPECIFIED.' RES/STA/VCE VALUES ARE /N OHMS) CAPAC/ TA/VCE VALUES ARE /N MICRO/'IRAM A T TORNE V Sept. 26, 1961 M. E. KRoM 3,002,054

TRUCK coNcENTRAToR RoR TELEPHONE ANSWERING SERVICE Filed Sept. 29, 1958 18 Sheets-Sheet 15 F IG. /4A EUR-FLOR (F/F) (UNLESS OTHERWISE SPECIFIED. RESISTANCE VALUES ARE /N OHMS,

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TRUCK CONCENTRATOR FOR TELEPHONE ANSWERING SERVICE Filed Sept. 29, 1958 18 Sheets-Sheet 17 F /G. /6A

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TRUCK CONCENTRATOR FOR TELEPHONE ANSWERING SERVICE Filed Sept. 29, 1958 18 Sheets-Sheet 18 F/G. 7A REcE/v/NG AMPL /F/EB (R) (UNLESS OTHERWISE SPECIFIED: RESISTANCE VALUES ARE /N OHMS, CAPAC/ANCE VALUE .S ARE /N MICROFARADS) @WAM/17W ATTO/PNE V United States Patent C 3,002,054 TRUCK CONCENTRATOR FOR TELEPHONE ANSWERHJG SERWCE Myron E. Krom, Convent Station, NJ., assigner to Bell Telephone Laboratories, Incorporated, New York, NX., a corporation of New York Filed Sept. 29, 1958, Ser. No. 764,143 13 Claims. (Cl. 179-27) This invention pertains to a switching system and, more particularly to a trunk concentrator designed for telephone answering service use.

Ever since the advent of the telephone, inventors have been concerned with developing new and improved ways of serving calls directed to telephones of absent subcribers. This development effort has produced two general methods of solution of the problem. The first method comprises the connection of a recorder to the telephone line of a subscriber desiring such service. 'Ihe recorder is usually located at the premises of the subscriber and, upon the reception of a call thereat during his absence, rst plays a prerecorded message advising the calling party that the called party is not available and that the calling party may, if desired, record a brief message stating the nature of his business. The second method comprises the connection of the subscribers line to a telephone answering service which answers his telephone and takes any incoming messages for him during his absence. Telephone answering systems offer an advantage over a mechanical recorder in that an operator answers each incoming call and can, in case of emergency, contact the absent subscriber, providing he left a forwarding telephone number, and advise him of the emergency.

Although telephone answering service is highly desirable, and in many cases preferable to a mechanical recorder, the use of such service has been impeded somewhat by the high cost of the trunks interconnecting the answering service center with the subscribers lines. The trunk cost has been high because, heretofore, it was usually necessary to provide an individual trunk pair to interconnect the answering service center with the central oiiice appearance of each subscriber line served by the answering service. This necessity forced answering services located in large metropolitan centers to adopt one of two modes of operation, neither of whichv was ideal. First, they could provide one large centrally located answering service center and then run an individual trunk pair from this center to the central oflice appearance of each observed subscriber line, regardless of how near or how far the central oices involved were located from the answering service center. This alternative resulted in high trunk costs for those subscribers whose central offices were remotely located from the answering service center. The second alternative available was to provide a plurality of smaller answering service centers, each of which was located as advantageously as possible so as to reduce trunk expenses. Ihe reduced trunk expenses in this alternative, however, were offset to some extent by the necessity of providing one or more operators at each location, regardless of how light the traffic may be.

it may, therefore, readily be seen that the ideal solution for an economical answering service system would be the provision of a single centrally located center in combination with a switching system which would reduce trunk costs by eliminating the necessity of providing an individual ltrunk pair between the answering service center and the central oice appearance of each observed line.

It is therefore an object of this invention to provide an improved switching system for use with an answering service.

It is a further object of the invention to provide a new ICC and improved switching system for reducing the trunk costs of telephone answering services.

It is a further object of the invention to provide an improved answering service switching system which eliminates the necessity of providing a separate pair of wires between the answering service center and each observed subscribers central office line appearance.

In accordance with the present invention, an electronic line scanner is provided in each central oice having subscriber lines that are to be served by the answering service. The scanner in each oice repeatedly and sequentially scans the plurality of lines under observation therein to derive information regarding the idle or ringing condition of each line. This information is transmitted to the answering service center where receiving equipment responds thereto and provides a continuous display of the condition of all lines under observation. An operator at the answering service center, upon noticing the ringing condition of an observed line, interconnects her position with the called line over a talking trunk common to all observed lines in the office to communicate with the calling subscriber.

A central otce is interconnected with the answering service center by a minimum of four trunk pairs of which three pairs are used for the interchange of timing and control signals between the two points, while the fourth pair is used as a talking trunk to connect the answering center operators position with any observed line to which a call is currently directed. The four trunk pairs enable the answering service center to monitor the idle or ringing condition of all lines under observation at a central oice and to answer any calls incoming thereto.

The system operation is controlled from the central oice by means of a pulse generator which comprises part of the scanner and which generates the timing pulses necessary for the system operation. The timing pulses drive a counter circuit having an operative position individual to each observed line. Thus, for example, if fifty lines are under observation at a particular central oce, the counter circuit thereat would have fifty operative positions for counting up to fifty. rIhe counter advances one position in response to each timing pulse.

The same pulses which drive the counter circuit at the central otiice are transmitted over the signaling trunks to the answering service center where they are applied to a counter circuit which is similar to the one in the central oice. 'Ihe pulses are applied to this counter in such a manner that it operates in synchronism with the one in the central oice.

The timing pulses at the central oice, together with the counter thereat, drive a matrix comprising a plurality of line scanning gates, one for each line under observation. Assuming again that there are ifty lines Vunder observation, there would be fty scanning gates numbered 00 through 49 which would be sequentially enabled by the timing pulses. There is a connection between each scanning gate and the observed line associated therewith whereby if at the time a particular gate, for example, scanning gate 02' is enabled, line 02 has ringing current thereon, gate 02 causes a pulse to be transmitted over the signaling trunks to the answering service center. rIhis pulse represents a ringing condition of line 02.

The counter in the answering service center drives a similar matrix having a gate individual to each counter position as well as individual to each line under observation at the central oice. Each gate is sequentially enabled as its associated counter position becomes operative. Remembering, that the counters in the central otlice and the answering center are in synchronism, the transmission of a ringing pulse to the answering center at the time line 02, for example, is scanned, causes this pulse to pass through the enabled gate at the answering :toegaat service center associated with line 02 and operate a utilization circuit which effects the energization of a signal device, of which there is an individual one for each line under observation, to indicate to the operator on duty that a call is currently being directed to this particular line.

The operator, upon observing the ringing signal, operates a switch individual to the observed line now being called, line 02 for example, which effects the necessary circuit actions to interconnect her position with the talking trunk interconnecting the answering service center and the central office in which this called line is located. The operation of this switch directs the output of the answering service gate matrix to one of the signaling trunks leading back to the cent-ral oifice. Then, during the next scan, the output pulse from the central office matrix gate associated with line y02 is directed Via this signaling trunk back to the central office.

Upon the reception of this pulse at the central oiiice, further circuit actions are effected to block the operation of the counter in the operative position associated with line 62. The counter thereby stops its operation and effects the operation of a relay network which interconnects the central office end of the talking trunk with called line 432, thereby enabling the operator at the answering service center to converse with the calling Party- After this connection is made, the counter, as well as the rest of the circuit, resumes its normal operation and resumes its scanning of the remaining lines for their busy or ringing condition. Thus, during the time the operator is answering a call, the circuit continues its operation and displays a signal at the answering service center each time a call is directed to additional ones of the observed lines.

It has been discussed how there are three signaling trunk pairs and one talking trunk pair interconnecting a central oice and the answering service center. This arrangement allows the answering service center y to answer only one call in a central office at a time. If it is desired to provide greater answering capacity for any central oiice, additional talking trunk pairs may be provided as needed. Each additional talking trunk pair will enable an additional operator at the answering center to answer other calls while a first operator is busy answering a prior call in the same oiiice.

A feature of the invention is the provision of a scanner for repeatedly ascertaining the ringing or idle condition of each of a plurality of lines and transmitting this information over a trunk to a distant point.

A further feature of the invention is the provision Of a scanner for repeatedly ascertaining the idle or ringing condition of each of a plurality of lines and transmitting the results of each scan over a trunk to a remote location where equipment thereat responds thereto and provides an indication of the idle or ringing condition of each line.

A further feature of the invention is the provision of a scanner for repeatedly testing the idle or ringing condition of a plurality of `lines at a iirst location together with a plurality of gates at a distant location which are enabled in synchronism with the scanner and which, in response to information received from the scanner, operate additional equipment to provide an indication of the ringing or idle condition of each line.

A further feature of the invention is the provision of a scanner for repeatedly testing the idle or ringing condition of a plurality of lines at a rst location and transmitting the results of each test over a trunk to a distant location having a plurality of gates which are enabled in synchronism with the scanner and which, in response to the information received over the trunk, operate associated equipment to provide an indication of the ringing or idle condition of each line.

A further feature of the invention is the provision ofA a scanner for repeatedly testing the idle or ringing condition of a plurality of llines in a central oli'ice and, in response to each test, for transmitting the results thereof to a remote center containing a plurality of control circuits, one for each line at the central oice, whereby upon the reception of this information from the central oiiice, the control circuit associated with a called line provides a means for redirecting a signal back to the central office which, in response thereto, blocks the operation of the scanner thereat and interconnects the called line with the remote location.

A further feature of the invention is the provision of a scanner for repeatedly testing the idle o-r ringing condition of a plurality of lines in a central oice and, in response to each test, for transmitting the results thereof to a remote center containing a plurality of control circuits, one for each line at the central office, whereby, upon the reception of this information lfrom the central office, the control circuit associated with a called line provides a means for redirecting a signal back to the central oice which, in response thereto, momentarily blocks the operation of the scanner thereat.

A further feature of the invention is the provision of a plurality of crosspoints comprising a matrix in combination with a corresponding plurality of lines together with means for sequentially enabling each crosspoint whereby a pulse is passed through a crosspoint when enabled if the line connected thereto is currently in a ringing condition.

A further feature of the invention is the provision of a plurality of crosspoints comprising a matrix in combination with a corresponding plurality of lines together with means for sequentially enabling each crosspoint whereby a signal is passed through a crosspoint when enabled and applied to a communication path if the line associated with the enabled crosspoint is currently in a ringing condition.

A further `feature of the invention is the provision of a plurality of lines in combination with a matrix having a corresponding plurality of crosspoints which are sequentially enabled whereby each line in a ringing condition at the time its associated crosspoint is enabled effects the transmission of a signal to a remote location containing equipment thereat which manifests the ringing or idle condition of each line.

A further feature of the invention is the provision of a plurality of lines in combination with a matrix having a corresponding plurality of crosspoints, one for each line, which are sequentially enabled whereby each line currently in a ringing condition at the time its associated crosspoint is enabled effects the transmission of a signal to a remote location containing equipment thereat which manifests the ringing or idle condition of each line and provides for the return of a signal to the central oiiice for eiiecting the interconnection of a called line with the remote location. v

These and other objects and features of the invention will be rnore readily understood when read in connection with the following detailed description and drawings in which:

FIGS. 1 through 7 together disclose the answering service switching system comprising the present invention;

FIGS. 8A and 8B disclose the circuit details of the enabling and inhibiting gates used throughout the present system;

FIGS. 9A through 9M show the various pulses produced by the scanner pulse generator circuit;

FIGS. l0 and 1l disclose the circuit details of the .scanner pulse generator;

FIGS. 12A, 12B, and 12C, respectively, disclose the circuit details, the functional symbol and the wave shapes, respectively, of the pulse amplifiers employed in the present system; 

